code: def save(self, path: str):
      faiss.write_index(self.index, path)
  
file_path: ludwig/ludwig/vector_index/faiss.py
imports: import faiss
  import numpy
  from ludwig.vector_index.base import VectorIndex
label_desc: Use image node_id 3 for calling the FaissIndex obj's underlying member method code with example usage: obj.save(path) without return types